- Telescope Drive AND Control System |
- Stellar Back-End Instrumention |
- Radio Astronomy Instrumentation |
- Site Site Survey Instrumentation
The Electronics Division of IIA has actively involved in the development of various Electronic Systems for use in the field telescopes. The major activities are covered in various sections as below:
I. Telescope Drive AND Control System:
1.1 Drive System
Precision Drive systems have been developed for different type of motors, which are used in our field- telescopes. The control system has also been implemented for
a) DC Servomotors
b) AC Synchronous motors
c) Stepper motors deployed in different telescopes.
Contact persons: V. Chinnappan
1.2 Dome Automation
Electronics Division has implemented automatic dome control system so that the slit in the dome is aligned to the pointing of the telescope at all times, doing away the laborious manual movement of the dome. This automation also helps in the initial setting of the dome position, to the pointing direction of the telescope. Such systems have been successfully implemented for the VBT, 1M Carl-Zeiss telescope in VBO and the HCT at Hanle.
Contact persons: V. Chinnappan, Faseehana Saleem
1.3 Remote Operation and Control of Telescopes
Remote operation of HCT has been achieved through a satellite link, provided by the Department of Space. This facility enables the operation of the telescope, dome and back-end instruments such as CCD and Faint Object Spectograph, from the observation center at CREST, Hosakote. The integrated software based on an Observarory-Server communicates with other Servers, each of which controls an individual sub-system. With the present communication bandwidth (1MBPS), data-downloads from the HCT takes about 200 seconds.
Contact persons: T. P. Prabhu
1.4 Solar Correlation Tracker
A Solar-feature correlation tracker has been built using commercially available components. The Tracker uses a DALSA 256*256 CCD camera, a frame-grabber board and a high-speed computation board procured from Coreco, Canada. A 3-axis piezoelectric actuator has been used to actuate the mirror. The software implements corrections at 250 Hz. A coarse tracker based on solar-limb tracking has also been installed.
Contact persons: A. V. Ananth, K. C. Thulaseedharan
1.5 Embedded Systems
Embedded systems play important role in modern distributed telescope control systems. 8-bit PIC controllers have been deployed as the motion control interface in the Gamma Ray Telescope array, being built at Hanle. Development work has also been initiated to implement state of the art CCD controllers, using 16-bit microcontrollers. The division has set-up a good laboratory for embedded system development.
1.6 Control Software for 75CM telescope at VBO
Based on the experience gained from the VBT and HCT, efforts are on to modernize the control system of the 75CM telescope at VBO. The concept is similar to the observatory control scheme used in HCT and implements client-server approach for the control of telescope, dome and guider. PMAC boards (Delta-Tau controls) and Siemens invertor, perform the actual control of the telescope and the dome.
Contact persons: A. V. Ananth, Anbzhalagan, Faseehana Saleem, J. S. Nathan
1.7 Control Software for White light Active Region Monitor (WARM) telescope
A control system is being implemented using MINT motion controller for the WARM telescope. The motors are A.C. servo motors from Baldor ,Germany. The control software is being developed under WINDOWS-NT.
Contact persons: K. C. Thulasidharan, A. V. Ananth
II. Stellar Back-End Instrumention :
2.1 Multi-channel Stellar Photo Polarimeter Data Acquisition System.
This instrument has been developed to measure the linear polarization of stars in the optical wavelengths covering from 0.4 to 0.85 µm for use in VBO telescopes in Kavalur. The desired wavelength region is selectable through various filters. The starlight is split into ordinary and extra-ordinary rays, by passing through a polarizer. By measuring the intensity of these rays at different orientations, the Stokes parameters will be calculated.
An embedded controller implements the instrument control and data acquisition from the polarimeter. A Graphical user interface has been developed in a personal computer, which communicates with the embedded system, through a serial link. The controller generates precise and synchronous timings, needed in the measurement of PMT data, corresponding to the ray photons. The acquired data is transmitted to the PC on demand. In addition to acquiring data, the controller monitors the health of the instrument and sends periodic-report to the user.
Contact person: G. Srinivasulu
2.2 CCD Camera Systems
The division has developed considerable expertise in implementing full camera system for large format CCDs. The cryo dewar operates efficiently with a liquid holding time of about 20 hours. The controller incorporates multi read-out, for fast read-out of frames and gives a low noise performance of 4-6-electron rms. The controller is implemented in DELPHI, operating under Windows.
Efforts are on for implementing data-acquisition system on a Linux platform, using IDL.
Contact persons: R. Srinivasan, G. Srinivasulu, A. V. Ananth, Arumugam
A prototype dewar based on Cryo-Tiger technology is also under development.
Contact persons: A. V. Ananth, Nagabhushana, Sagayanathan
III. Radio Astronomy Instrumentation:
3.1 Gauribidanur Radio Heliograph (GRH)
It is a T-Shaped radio interferometer array for dedicated observations of Solar Corona. It has 32 antenna groups. After analog signal processing, the signal from all groups are correlated in a 1024 channel digital back-end receiver. Correlated data is used for producing 2D images of solar corona.
3.2 Solar Radio Polarimeter
This instrument is used for obtaining the Stokes parameters of the polarized radio emissions from Solar Corona. The system consists of 4 antenna groups oriented at 0, 45, 90 and 135 degrees. Signals from above groups are processed in a back-end receiver system, to obtain the Stokes parameters.
3.3 DAS under Lab-View for Radio Spectrograph Observations
A radio spectrograph for observations of transient and energetic emissions from Solar Corona is ready for installation at Gauribidanur Radio Observatory. Data-Acquisition is planned using Lab-View software with real-time display.
Contact persons: M. S. Sundararajan, Faseehana Saleem
IV. Site Site Survey Instrumentation
4.1 Microthermal Monitoring System
Atmospheric seeing is due to wavefront perturbations caused by turbulence, occurring in thin horizontal layers, on a scale of several cm to meters. Turbulent mixing creates temperature and refractive index inhomogeneities on the same scale as the eddy sizes. Measuring these minute temperature fluctuations, and integrating over all turbulent layers in the atmosphere can determine the seeing. One such microthermal monitoring system has been built and successfully used in Hanle for measuring night time seeing. A project has been undertaken presently with the aim of applying microthermal measurement techniques, to the testing of a few selected potential solar observatory sites, in high-altitude locations in India.
contact persons: G. Srinivasulu, T. P. Prabhu.
4.2 Temperature Monitoring System for Telescope Building and dome
A temperature-gradient monitor system has been developed, based on a private network implemented with microcontrollers. The temperature sensor is a pre-calibrated digital semiconductor,DS1820. The temperature range of this sensor is -10 to +85ºC with a ± 0.5ºC accuracy. It is a standalone system with LCD display for showing the temperature. A network node can support up to 8 sensors and the system supports up to 8 nodes totaling 64 temperature sensors. To record long duration data, connectivity is provided to a PC through serial port. A 32 channel Temperature monitor has been installed in the VBT dome and has been working satisfactorily.
Contact persons: G. Srinivasulu, K. Ravi